3Com Switch 7700 Configuration Manual page 45

The system sets ports to inactive state if their basic configurations are different
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from the basic configuration of the active port with the lowest port number.
In a static LACP aggregation group, the system sets the ports to active or inactive
state based on these rules:
The system sets the port with the highest priority to active state, and others to
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inactive state based on the following descending order of priority levels:
full duplex/high speed
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full duplex/low speed
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half duplex/high speed
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half duplex/low speed
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If the Switch 7700 is connected to a peer device on which the maximum
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number of ports in a link aggregation is smaller than on the Switch 7700, the
Switch 7700 sets to active the number of ports that correspond to the peer's
maximum. The Switch 7700 sets its extra ports to inactive.
The system sets ports to inactive if they cannot aggregate with the active port
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with the lowest port number because of a hardware limit, for example, if
trans-board aggregation is not available.
The system sets ports to inactive if their basic configurations are different from
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the basic configuration of the active port with lowest port number.
Since a defined number of ports can be supported in an aggregation group, then
if the active ports in an aggregation group exceed the port quantity threshold for
that group, the system shall set some ports with smaller port numbers (in
ascending order) as selected ports and others as standby ports. Both selected and
standby ports can transceive LACP protocol, but standby ports cannot forward
user service packets.
Dynamic LACP aggregation
Dynamic LACP aggregation may automatic adding/deleting by the system but
prohibits manual configuration of users. Dynamic LACP aggregation can be
established even for a single port, as is called single port aggregation. LACP is
enabled at dynamic aggregation ports. Only the ports with the same speed,
duplex mode and basic configuration and connected to the same device can be
aggregated dynamically.
Since only a defined number of ports can be supported in an aggregation group,
then if the ports in an aggregation group exceed the port quantity threshold for
that group, the system shall set some ports with smaller system IDs (system priority
+ system MAC address) and port IDs (port priority + port number) as selected ports
and others as standby ports. If not, all member ports are selected ports. Both
selected and standby ports can transceive LACP protocol, but standby ports
cannot forward user service packets. Among the selected ports of an aggregation
group, the one with minimum port number serves as the master port for that
group and others are sub-ports.
In comparing system IDs, the system first compares system priority values; if they
are equal, then it compares system MAC addresses. The smaller system ID is
considered prior. Comparing port IDs comes in the same way: the system first
Configuring Link Aggregation 37